Apparatus for a non-contacting directional control of a web

ABSTRACT

A process for a non-contacting directional control of a web moving through a treating space comprises producing at least one stream of a treating fluid, which stream extends throughout the width of the web, supplying said stream of treating fluid to the web, baffling the treating fluid when it has been supplied to the web, uniformly distributing the baffled treating fluid over an exhaust cross-section, and then exhausting the treating fluid.

United States Patent Vits [4 Aug. 1,1972

[54] APPARATUS FOR A NON- CONTACTING DIRECTIONAL CONTROL OF A WEB [72] Inventor: l-lilmar Vits, Langenfeld, Germany [73] Assignee: Maschinenbau Vits GmbH [22] Filed: Sept. 28, 1970 [21] App1.N0.: 75,948

. [30] Foreign Application Priority Data Oct. 11, 1969 Germany ..P 19 51 345.2

[52] US. Cl ..34/156, 226/97 [51] Int. Cl ..F26b 13/00 [58] Field of Search ..34/10, 156; 226/97, 7, 196

[5 6] References Cited 9 UNITED STATES PATENTS 3,272,415 9/1966 Wallin ..226/97 3,384,282 5/1968 Vits ..226/97 3,324,570 6/1967 Flaith et al ..34/l 56 3,496,648 2/l970 Hering, Jr. ..34/156 3,060,594 lO/ 1 962 Meier-Windhorst ..34/1 56 Primary ExaminerFrederick L. Matteson Assistant ExaminerW. C. Anderson Att0rney-Michael S. Striker [5 7] ABSTRACT A process for a non-contacting directional control of a web moving through a treating space comprises producing at least one stream of a treating fluid, which stream extends throughout the width of the web, sup-v plying said stream of treating fluid to the web, baffling the treating fluid when it has been supplied to the web, uniformly distributing the baffled treating fluid over an exhaust cross-section, and then exhausting the treating fluid.

6 Claims, 3 Drawing Figures PATENTEDVAUG. 1 m2 SHEET 1 [IF 2 Fig.

a v v a I 1 M H In vento r.-

PATENTEDAUG 1 I972 3.680.223

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Fig. .3 I

Inventor APPARATUS FOR A NON-CONTACTING DIRECTIONAL CONTROL OF A WEB This invention relates to processes and apparatus for a non-contacting directional control of a web moving over closely spaced guiding means, which are preferably disposed only on one side of the web, for instance, in dryers in which exhaust spaces are provided between adjacent blow nozzles.

Processes for a non-contacting directional control of webs moving over guiding means consisting of blow nozzles are known and have been developed in various ways to ensure that webs which are sensitive owing to the material of the web and/or a coating thereon do not contact stationary parts because such contact would have detrimental results, such as scratches, cracks, tears and a separation of parts. A web is particularly sensitive when it is extremely thin, e.g., because it consists of tissue paper, or when it has a coating and the boundary layer at said coating should be maintained unchanged because a change of a solvent vapor atmosphere, e.g., may result in undesired changes of state. It may be necessary to ensure a non-contacting directional control of the web even when the guiding means are provided only on one side of the web so that there are on the free side of the web no influences which would give rise to undesired results. For instance, cushions of flowing air have been formed and have been used to support the web which is to be subjected to non-contacting directional control. In this case, a component of the movement of the flowing air may be imparted to the web so that the web is not only supported by and on cushions but is also moved and conveyed by such cushions. Besides, the treating fluid has been used in the form of hollow blown jets, which enclose spaces under a superatmospheric static pressure, and the web has been supported by such spaces so as to assume a non-contacting, floating state. The supporting and treating fluid has been flowed against flowguiding bodies, which are airfoil-shaped in cross-section so that the known aerodynamic properties of the airfoil section are utilized and the web is thus moved in a non-contacting manner through the treating space. Finally, such developments and refinements have not only been provided on the side where the supporting fluid is received but attention has also been directed to the exhausting of the treating fluid. Specifically, flowguiding bodies which are cylindrical or have an oval cross-section have been provided in the exhaust spaces for the supporting fluid, which generally consists of heated air in drying processes. It is the object of said cylinders to enforce an ordered flow and to minimize turbulence which would otherwise react on the flow conditions in the treating space with undesired effects on the measures adopted to move the floating web without flutter.

The present invention is based on the recognition that the provision of guiding surface elements, for instance, of convex flow-guiding bodies in the exhaust chambers for the supporting fluid, is not sufficient to meet the stringent requirements for the stabilization of the web in the treating space, particularly in the case of coated webs. To accomplish this object, it is not sufficient to provide flow-guiding bodies to be contacted by the exhausting supporting fluid, but additional measures must be adopted, which have been conceived on the basis of additional recognitions. One of these recognitions resides in that the provision of guiding means on only one side of the web will be sufficient only if these guiding means are very closely spaced, so that a formation of turbulence spots at the confluence of the exhaust flows from adjacent nozzles is inevitable. These turbulence spots exert an action in an upstream direction. Such action must be avoided and can be avoided when it is possible to damp said rebound effects. This can be accomplished if the supporting fluid is subjected in the exhaust space in that region thereof which immediately succeeds the nozzles to a slight, and subsequently eliminated compression relative to the subatmospheric pressures which prevail in the succeeding region so that the spent supporting fluid can be exhausted through such-succeeding spaces. Another requirement is to dissolve the undesired turbulence spots, which inevitably occur if the previously known means for the directional control of the web are used and the spacing of the nozzles or nozzle groups is much reduced. The requirements for a solution to the problem underlying the invention have now been stated. They reside in that the supporting fluid to be exhausted is initially baffled and is caused to be distributed uniformly or approximately uniformly over the exhaust cross-section and subsequently exhausted. The regions in which the pressure of the supporting fluid is temporarily increased in its absolute value, as a result of baffling, relative to the absolute value of the pressure in the succeeding regions are preferably those regions which receive streams of supporting fluid from different directions before such streams are combined. Such conditions are particularly found in nozzle dryers, in which double nozzles are arranged in a close succession in the direction of movement of the web. The confronting lips of such double nozzles give rise to a direct impact of streams of supporting fluid which are to be supported so that highly turbulent regions are created. The undesired effects of such turbulence cannot simply be eliminated in that the supporting fluid is sucked from these regions. On the contrary, the measures proposed according to the invention are required to preclude an undesired reaction into the treating space. Apparatus for carrying out the process, which comprise blow boxes and nozzle banks connected thereto, are characterized by the provision of throttling members which extend transversely through flow paths for exhausting the supporting fluid between the nozzle banks and consist in known manner of grids, nets, screens, grates, perforated plates, end walls, partitions, enclosing walls or the like. Perforated partitions will be used particularly where nozzle banks are provided which comprise a lip which faces the web with a boundary surface which is airfoil-shaped in cross-section. In such nozzle banks, two nozzle lips which immediately succeed each other in the direction of movement of the web may be arranged in mirror symmetry and one double nozzle or a plurality of additional double nozzles having spaced apart trailing edges of confronting nozzle lips may be provided between the first-mentioned nozzle lips to form one or more double nozzles of the kind described. Perforations have the special advantage that the selection of their positions and/or spacing and the use of perforations having varying cross-sectional areas will enable the selection of a desired throttling effect per unit of the perforated area so that even with irregularly confined exhaust spaces resulting in highly different exhaust flow velocities over the exhaust cross-section the exhausting supporting fluid may be distributed in the desired manner as uniformly as possible over the exhaust cross-section. For instance, where guiding walls are provided which are perforated and extend at a generally constant distance from the confronting nozzle lips and contact each other in the center plane of respective nozzle groups consisting of the two double nozzles, the above mentioned varying arrangement of the perforations and their cross-sections may be selected to ensure perfectly ordered conditions of flow in the succeeding region of the exhaust spaces.

The above-mentioned perforations need not consist of individual apertures in the form of bores but may be partly combined in slots. Such slots may preferably extend along the center plane of a nozzle group consisting of two double nozzles.

An arrangement of the kind mentioned last has been used in the embodiment of the invention which is shown by way of example in the drawing, which is a vertical longitudinal sectional view showing a nozzle group consisting of two double nozzles.

In the drawing,

FIG. 1 represents the above-mentioned sectional view,

FIG. 2 shows how perforations may be combined in a slot, and

FIG. 3 represents the dependence of the pressure and thrust on the distance of the web from a nozzle arrangement.

The drawing indicates in the first place the dash-dot line 1, in which the center line of the web, not shown, intersects the plane of the drawing so that this center must be considered a representation of the web itself. The nozzle boxes 2, 3 are disposed below the web and may be succeeded by additional nozzle boxes, not shown, which are provided with additional nozzle groups and which are relatively closely spaced. The nozzle boxes are connected to a supporting fluid duct, which is not shown and which supplies supporting fluid under a superatmospheric pressure into the cavities of the blow boxes. This is indicated by a -llsign in the drawing. The blow boxes 2, 3 are succeeded by the nozzle bodies 21, 22 and 31, 32, which are continued by the perforated nozzle lips 23, 24 and 33, 34. As is apparent from the profiles represented by dash-dot lines, these nozzle lips are airfoil-shaped in cross-section. Perforated transverse ribs 4 and 5, which have concave depressions facing the web, are provided at the transitions between the nozzle bodies 21, 22; 31, 32 and the nozzle lips 23, 24,33, 34. In this way, the nozzle lips 23, 24 and the transverse rib 4, and the nozzle lips 33, 34 and the transverse rib 5, form the slot nozzles 6, 7 and 8, 9 of respective double nozzles 6, 7 and 8, 9. The means described thus far and shown on the drawing are already known.

The use of the confronting nozzle lips 24 and 33 results in a high turbulence in the region 10, in which the streams of supporting fluid impinge which are conducted between the web having a center plane indicated by the line 1, and the nozzle lips 24 and 33. The resulting turbulent spots have such a strong and undesired influence on the flow conditions described hereinbefore that the resulting dynamic pressure lifts the web from the nozzle into an undesired elevated position. The means provided by the invention are required to eliminate this influence. For this purpose throttling means comprising, guiding surface elements 11 and 12, which are approximately equi-distant or substantially parallel to the nozzle lips 24, 33, are disposed below the turbulent region or exhaust space 10 and in the center plane between the blow boxes 2, 3 and the double nozzles 6, 7 and 8, 9 connected thereto contact in a line 13. The guiding surface elements ll, 12 which together form a throttling wall consist of perforated guide plates, which may be joined by welding, e.g., at 13, and are joined to the nozzle body walls 22 and 31 by suitable seam welds.

This arrangement produces the desired results which have been explained in detail hereinbefore.

The invention will afford particular advantages when it is necessary to maintain a boundary layer of the solvent vapor atmosphere of a coating of the web on the side thereof which is remote from the nozzle. Even if the perforated guiding surface element is provided only on one side of the web, the turbulence occurring in the exhaust region of the treating fluid will not react on the treating space so that the boundary layer will also remain unchanged. This will be essential if the quality of the treated product depends on the suppression of a flow of the boundary layer until the treatment has been terminated.

FIG. 2 shows a modification of FIG. 1. In FIG. 2, the perforations are combined along line 13 in a nozzle slot 16. Besides, it is apparent from FIG. 2 that the distances 17, 18, 19 progressively increase toward the side walls 22, 31 of the blow boxes so that in conjunction with the configuration of the exhaust region 10 the exhausting supporting fluid will be uniformly distributed over the guiding surface elements ll, 12 and over the exhaust cross-section.

FIG. 3 illustrates the resulting conditions in a graph, in which the pressure and the thrust applied by the supporting agent to the web are plotted along the axis of ordinates and the distance of the web from the nozzles is plotted on the axis of abscissas. For an approximate representation of the orders of magnitude involved, it may be stated that the highest pressure represented on the axis of ordinates is about 5 kilograms per square meter. The distance 0 represented in the drawing has an order of magnitude of about 2 millimeters. The axis of abscissas represented by a solid line I will be obtained if the above-mentioned, relatively small spacing between the nozzle exists and if the supporting fluid is exhausted in the manner shown in FIG. 1. If nozzles having the conventional spacing were provided, the axis of abscissas would assume the position represented by the dashdot line II. This nozzle spacing could be adopted if the guiding means for maintaining the web at a predetermined distance from the nozzles could be provided on both sides of the web. Without the measures represented in FIG. 1,, the position of the axis of abscissas would be downwardly displaced by the value a represented in the drawing so that the axis of abscissas would assume an abnormal position, in which it coincides withthe dash-dot-dot line III. In spite of a close spacing of the nozzles, the means shown in FIG. 1 enable a displacement of the axis of abscissas from the extremely low position by the distance b upwardly to the normal position I so that a characteristic curve will be obtained even where nozzles are used in the conventional arrangement, with a normal spacing.

It is apparent from FIG. 1 of the US. Pat. specification No. 2,594,299 how nozzles designed according to the invention may be arranged as a floating dryer relative to a floating web which is moved through a treating space and treated in this condition.

The invention is directed to each of the features stated, even though it may have' been mentioned only in conjunction with additional features, as well as to any practicable combination of parts of the features and finally to the combination of all features, provided that the individual features or the combinations of parts or all of the features have technical utility and are practicable and useful, even though novel technical results which are obtained have not been mentioned or specifically described. All details which are apparent and have been stated in the specification and/or claims and/or shown in the drawing and any combinations of such details are considered as described and claimed as such, in their function or functions and in the functional relation or functional relations in combinations of part or all of said details.

What is claimed is:

1. Apparatus for non-contacting guiding of a moving web through a treating space comprising at least one blow box for receiving a treating fluid; a nozzle extending throughout the width of the web and being connected to the blow box for blowing the treated fluid against the web, said nozzle having a nozzle-forming wall comprising an extension in the form of a nozzle lip which forms a guiding surface for the treating fluid and has an airfoil-shaped outline; an exhaust space defined by the web and laterally of said nozzle wall into which the treating fluid supplied to the web passes; an exhaust conduit communicating with said exhaust space for exhausting said treating fluid therefrom; and throttling means comprising a throttling wall extending through said exhaust space transversely to the direction of flow of the treating fluid to be exhausted and having apertures for throttling said treating fluid, said throttling wall being substantially parallel to said nozzle lip.

2. Apparatus for non-contacting guiding of a moving web through a treating space comprising a plurality of adjacent blow boxes for receiving treating fluid; a plurality of nozzles extending through the width of the web and respectively connected to said blow boxes for blowing a treating fluid against the web, each of said nozzles having a nozzle-forming wall comprising an extension in the form of a nozzle lip which forms a guiding surface for the treating fluid and has an airfoilshaped outline; an exhaust space into which the treating fluid supplied to the web passes and being defined by the web and nozzle walls of nozzles on adjacent nozzle boxes; an exhaust conduit communicating with said exhaust space for exhausting said treating fluid therefrom; and throttling means comprising a throttling wall extending through the exhaust space transversely to the direction of flow of the treating fluid to be exhausted and having apertures for throttling the treating fluid, said throttling wall being substantially parallel to the nozzle lips on adjacent nozzles.

3. Apparatus as defined in claim 2, wherein said apertures in said throttling wall comprise nozzles.

4. Apparatus as defined In claim 2, wherein said throttling wall consists of a connection between facing walls of two nozzles succeeding in the direction of movement of the web.

5. Apparatus as defined in claim 2, wherein said nozzle boxes, said nozzles, said nozzle lips and said throttling wall are mirror symmetrically arranged with regard to a plane of symmetry between adjacent nozzles.

6. Apparatus as defined in claim 2, wherein each of the nozzle lips has a convexly curved surface facing the web and a thin edge at the free end thereof. 

1. Apparatus for non-contacting guiding of a moving weB through a treating space comprising at least one blow box for receiving a treating fluid; a nozzle extending throughout the width of the web and being connected to the blow box for blowing the treated fluid against the web, said nozzle having a nozzle-forming wall comprising an extension in the form of a nozzle lip which forms a guiding surface for the treating fluid and has an airfoil-shaped outline; an exhaust space defined by the web and laterally of said nozzle wall into which the treating fluid supplied to the web passes; an exhaust conduit communicating with said exhaust space for exhausting said treating fluid therefrom; and throttling means comprising a throttling wall extending through said exhaust space transversely to the direction of flow of the treating fluid to be exhausted and having apertures for throttling said treating fluid, said throttling wall being substantially parallel to said nozzle lip.
 2. Apparatus for non-contacting guiding of a moving web through a treating space comprising a plurality of adjacent blow boxes for receiving treating fluid; a plurality of nozzles extending through the width of the web and respectively connected to said blow boxes for blowing a treating fluid against the web, each of said nozzles having a nozzle-forming wall comprising an extension in the form of a nozzle lip which forms a guiding surface for the treating fluid and has an airfoil-shaped outline; an exhaust space into which the treating fluid supplied to the web passes and being defined by the web and nozzle walls of nozzles on adjacent nozzle boxes; an exhaust conduit communicating with said exhaust space for exhausting said treating fluid therefrom; and throttling means comprising a throttling wall extending through the exhaust space transversely to the direction of flow of the treating fluid to be exhausted and having apertures for throttling the treating fluid, said throttling wall being substantially parallel to the nozzle lips on adjacent nozzles.
 3. Apparatus as defined in claim 2, wherein said apertures in said throttling wall comprise nozzles.
 4. Apparatus as defined in claim 2, wherein said throttling wall consists of a connection between facing walls of two nozzles succeeding in the direction of movement of the web.
 5. Apparatus as defined in claim 2, wherein said nozzle boxes, said nozzles, said nozzle lips and said throttling wall are mirror symmetrically arranged with regard to a plane of symmetry between adjacent nozzles.
 6. Apparatus as defined in claim 2, wherein each of the nozzle lips has a convexly curved surface facing the web and a thin edge at the free end thereof. 